The proposed program will evaluate rheological parameters as diagnostic indices for diseases related to or produced by altered blood flow. It is hoped to achieve a close working relationship between basic research scientists and practicing physicians in a clinical setting where such specialized equipment is rarely available. Clinical hemorheology will be applied in depth to three areas where the probability of establishing significant findings is high. The diagnostic and predictive potential of blood viscosity related factors will be examined in: a) screening of patients with arteriosclerotic cardiovascular disease; b) examination of patients with markedly elevated plasma viscosities; c) rheological survey of subjects for contraindication to oral contraception. Blood viscosity related factors to be examined include: a) viscosity of anticoagulated blood, washed red blood cells and plasma as a function of rate of shear; b) deformability of the red blood cells; c) internal viscosity of the red blood cells; d) quantitative measure of degree of aggregation under specific conditions; e) hematocrit and mean corpuscular hemoglobin concentration; f) erythrocyte sedimentation rate; g) concentrations of plasma fibrinogen, fibrin monomer and serum fibrinogen breakdown products; and h) plasma protein(s) level(s). Precise knowledge of blood viscosity related factors should ultimately enable the design of improved diagnostic tests and therapeutic manipulations to produce selective modification of deviant rheological parameters.